Dark matter has been making more headlines than an A-list celebrity in Hollywood over the course these past few months. This might be because the scientific community finally produced an “image” of the elusive substance, fueling our peer-reviewed paparazzi expectations. But what exactly is dark matter and why is it so intriguing?

The brief video below by Minute Physics touches on a few key concepts surrounding dark matter, including how scientists noticed that the universe behaved far differently than they had expected. While researchers expected stars at the far end of a galaxy to taper off in speed and ultimately leave from their galactic orbits, they observed something quite different. The stars as the ends of galaxies actually accelerated to remain in orbit, suggesting that something was providing a strong enough gravitational force to keep them in check.

The University of Arizona. Left: Theorized galaxy spin without dark matter. Right: How galaxies spin.

Minute Physics goes on to explain that this something, which scientists refer to as dark matter, is four times more common in the universe than visible matter and why it’s necessary.